The present invention relates to a carbon black for a tire tread rubber capable of imparting an excellent abrasion resistance and traction performance to a rubber component.
In recent years, with an improvement in the performance of automobiles, demands for the performances and ride comfort at high speeds have been increased, and research and development have eagerly been conducted on an improvement in the performance of the tire tread portion.
For this reason, a carbon black for reinforcement of rubber as well has strongly been required to have such characteristics that it can simultaneously impart to a rubber component a high abrasion resistance sufficient to attain ride comfort at high speeds and a high traction performance capable of providing a high grip of the road surface.
The reinforcement of rubber with carbon black has hitherto been thought to be mainly governed by the specific surface area (particle diameter) and structure of the carbon black. In general, the better the above-described characteristics, the larger the increase in the abrasion resistance of the compounded rubber.
The use of SBR having a high styrene content as a rubber component of a tread portion and the compounding of a process oil in high loading are known as means for improving the grip of the road surface.
However, the above-described use of SBR having a high styrene content and compounding of a process oil bring about not only the sufficient improvement in the traction performance but also a remarkable lowering in the abrasion resistance.
In view of the above, the present inventors have forwarded studies on the impartation of a high traction performance to a rubber component without detriment to the high abrasion resistance from various angles in respect of characteristics of carbon black and, as a result, have found that it is effective in attaining this purpose to narrow the aggregate size distribution of carbon black, lower the surface activity and decrease the Stokes diameter of an aggregate size relative to the electron-microscopic average diameter of carbon black, which has led to the completion of the present invention.